Conflicting versions of datanucleus enhancer in a maven google app engine project - google-app-engine

Question

I'm having a problem setting up datanucleus enhancer to use with a google app engine project. If I use the datanucleus eclipse plugin everything goes well, but in my maven project I get a strange conflicting version error.
My POM has these datanucleus references:
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>1.1.0</version>
</dependency>
...
<plugin>
<groupId>org.datanucleus</groupId>
<artifactId>maven-datanucleus-plugin</artifactId>
<version>1.1.0</version>
<configuration>
<mappingIncludes>**/*.class</mappingIncludes>
<verbose>true</verbose>
<enhancerName>ASM</enhancerName>
<api>JDO</api>
</configuration>
<executions>
<execution>
<phase>compile</phase>
<goals>
<goal>enhance</goal>
</goals>
</execution>
</executions>
</plugin>
When I try to build the project I get the following error:
Exception in thread "main" Plugin (Bundle) "org.datanucleus" is already registered.
Ensure you dont have multiple JAR versions of the same plugin in the classpath. The URL "file:/Users/drome/.m2/repository/org/datanucleus/datanucleus-core/1.1.0/**datanucleus-core-1.1.0.jar**" is already registered, and you are trying to register an identical plugin located at URL "file:/Users/drome/.m2/repository/org/datanucleus/datanucleus-core/1.1.3/**datanucleus-core-1.1.3.jar**."
org.datanucleus.exceptions.NucleusException: Plugin (Bundle) "org.datanucleus" is already registered. Ensure you dont have multiple JAR versions of the same plugin in the classpath. The URL "file:/Users/drome/.m2/repository/org/datanucleus/datanucleus-core/1.1.0/datanucleus-core-1.1.0.jar" is already registered, and you are trying to register an identical plugin located at URL "file:/Users/drome/.m2/repository/org/datanucleus/datanucleus-core/1.1.3/datanucleus-core-1.1.3.jar."
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:437)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:343)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensions(NonManagedPluginRegistry.java:227
)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensionPoints(NonManagedPluginRegistry.jav
a:159)
at org.datanucleus.plugin.PluginManager.registerExtensionPoints(PluginManager.java:82)
at org.datanucleus.OMFContext.(OMFContext.java:164)
at org.datanucleus.enhancer.DataNucleusEnhancer.(DataNucleusEnhancer.java:171)
at org.datanucleus.enhancer.DataNucleusEnhancer.(DataNucleusEnhancer.java:149)
at org.datanucleus.enhancer.DataNucleusEnhancer.main(DataNucleusEnhancer.java:1157)
I don't understand why datanucleus required maven to download datanucleus-core-1.1.3.jar since this is not referenced in the pom.xml
I also do not understand why datanucleus-core-1.1.3.jar is being registered...
Any ideas?
Thanks in advance...

Answer 1

The DN M2 plugin pulls in the latest versions of the available DN jars that it needs to do its job (there is no other sensible way to do it other than use the latest). You want to restrict "core" to a different version, either by specifying the plugin dependency of core, or by specifying that in your application to
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>1.1.0</version>
<scope>runtime</scope>
</dependency>

Answer 2

Unfortunately the answer is "hidden" in the comments:
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>1.1.0</version>
<scope>runtime</scope>
</dependency>
That worked for me!

Answer 3

I ran into the same issue while testing a maven gae plugin archetype.
I fixed it by adding exclusions in my gae runtime transitive dependencies
<!-- Google App Engine meta-package -->
<dependency>
<groupId>net.kindleit</groupId>
<artifactId>gae-runtime</artifactId>
<version>${gae.version}</version>
<type>pom</type>
<exclusions>
<exclusion>
<groupId>com.google.appengine.orm</groupId>
<artifactId>datanucleus-core</artifactId>
</exclusion>
</exclusions>
</dependency>
and then adding the nucleus core as a runtime dependency
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>${datanucleus-core.version}</version>
<scope>runtime</scope>
<exclusions>
<exclusion>
<groupId>javax.transaction</groupId>
<artifactId>transaction-api</artifactId>
</exclusion>
</exclusions>
</dependency>
as keeping the gae plugin section simple:
<plugin>
<groupId>org.datanucleus</groupId>
<artifactId>maven-datanucleus-plugin</artifactId>
<version>${maven-datanucleus-plugin.version}</version>
<configuration>
<!--
Make sure this path contains your persistent classes!
-->
<mappingIncludes>**/model/*.class</mappingIncludes>
<verbose>true</verbose>
<enhancerName>ASM</enhancerName>
<api>JDO</api>
</configuration>
<executions>
<execution>
<phase>compile</phase>
<goals>
<goal>enhance</goal>
</goals>
</execution>
</executions>
</plugin>

Answer 4

After reading "How to override a plugin's dependency in Maven", I found another way to fix this. Here is my POM:
<plugin>
<groupId>org.datanucleus</groupId>
<artifactId>maven-datanucleus-plugin</artifactId>
<version>3.1.0-m3</version>
<configuration>
<verbose>true</verbose>
</configuration>
<executions>
<execution>
<phase>process-classes</phase>
<goals>
<goal>enhance</goal>
</goals>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>3.0.4</version>
</dependency>
</dependencies>
</plugin>

Answer 5

clearing your old version of datanucleus from your local maven repository also solving the problem.

Answer 6

Maven-datanucleus-plugin has stopped pulling in the latest versions of the available datanucleus-core since version 3.1.1.
Check the differences between the POM files for Maven-datanucleus-plugin 3.1.1 (http://repo1.maven.org/maven2/org/datanucleus/maven-datanucleus-plugin/3.1.1/maven-datanucleus-plugin-3.1.1.pom) and 3.1.0-release (http://mvnrepository.com/artifact/org.datanucleus/maven-datanucleus-plugin/3.1.0-release).
For maven-datanucleus-plugin 3.1.1 the version range of datanucleus-core dependency is (3.0.99, 3.1.99), and for maven-datanucleus-plugin 3.1.0-release it is (3.0.99, ). No wonder for the older versions of maven-datanucleus-plugin, it automatically pulls in the latest versions of datanucleus-core.